Role of pesticides in hepatocarcinogenesis.

Pesticides are biologically active substances that are significant environmental contaminants. Only a few of the many pesticides have been subjected to short- or long-term carcinogenicity tests. To date, 16 of them have been identified as hepatocarcinogenic agents in animals, usually mice. However, their cancer-inducing effect in humans has not been completely proved. The use of short-term screening tests (first of all the Salmonella-microsome test) for routine screening of pesticides on a large scale is highly recommended. The herbicide 2,4,5-trichlorophenoxyethanol (TCPE) containing different amounts of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was tested for carcinogenicity in Swiss mice. TCPE enhanced liver tumors in males but TCDD did not affect liver tumor incidence. The occurrence of liver tumors was shown to be dose-dependent. There was no correlation between the results of in vivo carcinogenicity studies and the induction of aryl hydrocarbon hydroxylase and biphenyl 2-hydroxylase activities.